Apparatus for laminography



Dec. 13, 1949 R. J. STAVA APPARATUS FOR LAMINOGRAPHY 9 Sheets-Sheet 1 Filed June 15, 1944 haven-r011 Roaawr JI f'DTAvA BY H 1) M W fi-rry'a.

Dec. 13, 1949 R. J. STAVA APPARATUS FOR LAMINOGRAPHY 9 Sheets-Sheet 2 Filed June 15, 1944 Dec. 13, 1949 R. J. STAVA 2,491,224

APPARATus FOR LAMINOGRAPHY BY WWW A'rromvavs.

Dec. 13, 1949 R. J. STAVA 2,491,224

APPARATUS FOR LAMINOGRAPHY Filed June 15, 1944 9 Sheets-Sheet 6 INVLNTOR. RQBERT J. 15mm BY H7614 MM),

Dec. 13, 1949 R. J. STAVA 2,49l 224 APPARATUS FOR LAMI NOGRAPHY Filed June 15, 194 I 9 Sheets-Sheet 7 F A v-v :44 45 4| 7 fiTToRnua Dec. 13, 1949 J sT v 2,491,224

APPARATUS FQR LAMINOGRAPHY Filed June 15, 1944 9 Sheets-Sheet 8 Emmi 0 y as t 2? FIG. 17,

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ROBERT J S7 v ATTORN EYE Dec. 13, 1949 R. J. STAVA APPARATUS FOR LAMIN OGRAPHY F le i June 15, 1944 Sheets-Sheet 9 a t I i 2 a I! i:

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Patented Dec. 13, 1949 APPARATUS FOR LAMINOGRAPHY Robert J. Stava, University Heights, Ohio, as-

signor to Picker X-Ray Corporation, Waite Manufacturing Division, Inc., Cleveland, Ohio, a corporation of Ohio Application .llune 15, 1944, Serial No. 540,480

17 Claims.

This invention relates to improvements in drive and control means for apparatus used in laminography.

My invention is utilized in connection with a-pparatus in which an X-ray tube and a sensitized plate holder are mounted for reciprocation or oscillation on opposite sides of a body to be viewed or photographed. In this type of apparatus, the focal point or focal plane is fixed at the level of body section to be viewed and oscillation of the tube and plate holder during radiography causes a fogging of all layers not in the focal plane. It is necessary that this oscillation be of fairly large amplitude if the plane photographed is to represent a very thin layer of body tissue. A shorter amplitude photographs a thicker layer, and an amplitude greater than that herein provided is of little value. It is desirable that the apparatus oscillating the tube and plate holder have uniform linear motion during the period the photograph is taken.

An object of the present invention is to provide a novel drive means for oscillating the tube and plate holder in such an apparatus and partic ularly one in which the driving means moves in a continuous or endless elongated path and wherein the driving means is given uniform linear motion along a portion of said path. Means is provided operable while the drive means is moving with uniform linear motion to initiate the taking of the photograph, and this last named means is variable in its action so as to provide for various lengths of exposure required.

My invention provides also, in addition to the features mentioned in the preceding paragraph, means for varying the speed of the drive means so that wide range of variable exposures is provided by the combination of varying speeds and varying lengths of exposure along the path of travel of the drive means.

It should be understood that the X-ray tube and the plate holder together with their necessary supports and attached electrical cables provide apparatus of considerable weight. My improved drive means is provided with means for reducing its speed as the drive means passes around reverse bends at the opposite ends of its elongated path of travel.

Novel means is provided for coordinating the setting of the governor speed for the electrical motor connected with the driving means and for adjusting a resistance in said motor circuit to be cut into and out of the motor circuit as the driving means reverses its direction of movement at opposite ends of its path of travel.

My invention also provides a simple arrangement connected with the above-described apparatus whereby stereoscopic radiographs may be taken utilizing the same apparatus. To this end, novel means is provided for insuring that the drive means always stops in a fixed position, and means is provided for moving the drive means a limited distance along its path of travel from said fixed stopping point when taking stereoscopic pictures.

Other novel features of my invention will be found in the arrangement of the various parts for carrying out the above-described purposes and in the electrical control circuit-s for producing the various results explained, together with novel arrangements of cams and switches, motor drives, governor controls, rheostats and the like for producing the desired results. All of these features will be fully described in the specification, and the essential features thereof will be set forth in the appended claims.

In the drawings,

Fig. 1 is a perspective view of X-ray apparatus equipped with my improved device with the top of the table removed for a better understanding of the apparatus;

Fig. 2 is a front view of the device shown at the left end of the table of Fig. i with a portion of the cover plate removed to more clearly show the drive means;

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2;

Fig. 4 is a rear view of the device of Fig. 2 with the covers removed to more clearly show the parts;

Fig. 5 is a iragmental sectional view taken along the line 5-5 of Fig. i;

Fig. 6 is a vertical sectional view taken along the line ii6 of Fig. 4;

Figs. '1' and 8 are fragmental sectional views taken along similarly numbered lines of Fig. 6;

Fig. 9 is a top plan view of the device of Figs. 2 and 4;

Fig. 10 is a fragmental sectional view taken along the line Iii-l i! of Fig. 4;

Fig. 11 is an elevational view of the X-ray tube mounting bracket seen near the tube in Fig. 1;

Figs. 12 and 13 are sectional views taken along similarly numbered lines of Fig. 11;

Fig. 14 is an elevational view of the apparatus connected to the side of the table near the plate holder of Fig. 1 with parts broken away to more clearly show the construction. Figs. 15 and 16 are sectional views taken along similarly numbered lines of Fig. 14;

Fig. 17 is a perspective view showing my device connected with the X-ray tube supporting column near the ceiling instead. of the mounting near the table shown in Fig. 1; while Fig. 18 is a wiring diagram showing the electrical connections for my device.

In Fig. 1 I have shown a general view of X-ray apparatus equipped with my new device. This apparatus includes a table intended to be provided with the usual top on which a patient lies during examination, but this top has been removed to more clearly disclose the present invention. Beneath the table top riding upon suitable rails 2i is a plate holder 22 provided with rollers 23 resting on the rails. This plate holder is provided with an extension bracket 22a. which projects beyond the edge of the table and carries a pivotally mounted friction-reducing bearing member 24, the details of which are best seen in Figs. 14 and 15. A pin 25 pivotally connects bracket 22a and plate 24. The pin 25 is in the center of the plate and is vertically adjustable in the slot in bracket 22a. On theoppcsite side of plate 24 are pivotally mounted four concave rollers 26 mounted in a common plane and having a curvature generally corresponding to the diameter of oscillating lever 21. Referring again to Fig. l, a carriage or column 23 is mounted for movement lengthwise of table 2! To this end bars 29 and 38 are supported between brackets 20a which are connected to the opposite ends of the table 28. The column 23 at its base is provided with friction-reducing rollers which bear upon these two bars so that the column is readily moved backward and forward lengthwise of the table.

Referring to Figs. 11, 12, and 13 together with Fig. 1, the column 28 has mounted within it an upright tube 3| on which is mounted a bracket for travel vertically along the tube. Pivotally mounted on this bracket is a U-shaped arm adapted to oscillate about pivot 3 The arm 33 carries a plurality of rods 35 on which is mounted an Y-ray tube 36. This tube is ener-- gized through a pair of high tension cables 3! which preferably pass over rollers 38 at the top of column 28. The X-ray tube is provided with the usual accessories and adjustments which need not be described here as they are well-known to those skilled in the art. Secured to the arm 33 is a bracket 39, the rear end of which provides a sleeve embracing the oscillating lever 2'1. A thumb screw 48 looks the lever 21 to the bracket 39.

The above-described apparatus provides on opposite sides of the body to be photographed the plate holder 22 and an X-ray tube 36 mounted for oscillation. Means is provided for fixing the pivotal point for lever 21 in the desired focal plane of the body section to be viewed or photo graphed. Referring to Figs. 1, 14, 15, and 16, a stand 4| is fixed to the side of table 29 by means of thumb screws 42. Thus, this stand is adjustable lengthwise of the table. In this stand are supported a vertically extending rod 43 and a parellel screw 44 rotatably mounted in the stand 45. A bracket 45 has threaded engagement with the screw 44 and has a U-shaped portion 45a slidably embracing the rod 23 as best seen in Fig. 16. Means is provided for rotating the screw 45, this means comprising a pair of mutually engaging beveled pinions 46 one fixed on screw id and the other rotatably mounted in the stand ll and provided with the crank handle 47. Thus by rotating the handle 41 screw 44 is rotated and bracket is caused to move vertically in the stand 4|. A pointer 45b extends through a slit 2 la in the stand 4! so as to visually indicate the position of the movable pivot 58. This pivot connects bracket 45 with sleeve 49 which slidably embraces lever 27. It will be apparent from the-above-description that with the pivot 48 fixed at the desired level, the column 28 may be moved backward and forward and in so doing it will cause the X-ray tube to oscillate about pivot 34 in bracket 32 while plate holder 22 will oscillate in the opposite direction beneath the body of the patient so that a picture may be taken, on the sensitized plate carried in the holder 22, of the body section at the level of the pivot 48 while all other layers of the body will be fogged.

My invention provides novel means for causing the movement of the column 28 backwards and forwards along the bars 29 and 36. The device is indicated within the housing 50 at the left'end of bar 29 in Fig. 1 and clamped to said bar by means of the clamping member 5|. Referring to Figs. 4 and 5, suitably mounted within the housing is an electric motor 52 which drives shaft 53 and through suitable reduction gearing drives the worm wheel 54 which in turn is keyed to shaft 55 on which is fixed sprocket 55. A'chain 51 connects sprocket 56 with sprocket 56 (see 2) which is rotatably carried by a bracket 59 which is mounted by means of bolts 50 for adjustment along the slot 6| in a portion of housing 56 as best seen in Fig. 9.

Driving means is provided between chain 5'? and the column or carriage 28. This means cornprises a cross-head pin 62 carried by chain 51 with the head of the pin vertically reciprocable in a cross-head slide '63 which is best seen in Figs. 2, 3, 5, and 6. This cross-head slide has parts 63a and 63?) located respectively inside and outside of a plate 55a which forms part of the housing 52. A gib 63c slides along the slotted opening 56b in the plate 50a, all of the parts 63a, 63b, and $30 being held together by the bolts 64. On the outside portion 63b of thecrosshead slide is carried an ear 63d through which passes a rod 65 held in place by the nuts 65. The other end of the rod 65 is adjustably secured in a clamp 28a secured to column 28 as best seen in Fig. 1. It results from this construction that when motor 52 is operated chain 51 travels about the sprockets 56 and 58 carrying cross-head pin 62 first toward the right as viewed in Fig. 2 along the top run of chain 51, then as pin 62 goes around sprocket 53 in the direction of the arrow there indicated, the cross-head pin will move downward in the cross-head slide while the slide dwells at the right-hand end of its travel after which pin 62 will return toward the left along the bottom run of chain 5'1 until it passes around sprocket 56 when the pin again travels vertically upward in the slide while the slide dwells at the left end of its run after which pin 62 will again move toward the right along the top run of the chain returning to the starting point. It is during sucha cycle of operation that my laminographic apparatus is operated to produce an X-ray picture as will presently be described.

Means is provided for varying the speed of motor 52 so as to vary the speed of travel of cross-head pin 62 as it follows the path of endless chain 51. Any suitable means may be uti lized for this purpose, but I have illustrated in Fig. 4 the construction shown in Patent 2,291,639

granted August 4, 1942, to Royal Lee to which reference may be made for a more complete description if one is desired. It is sufficient to state here that the pair of contacts 6'! in the energizing circuit of motor 52 (as will be later described in connection with Fig. 18) are separated when the motor speed exceeds the predetermined speed by the action of weight 68 about pivot t9. This places resistors iii in series with the windings ii and 52 of motor 52 so that it slows down. Actually the contacts 61 flutter at a high frequency and the speed of motor 52 is held nearly constant. In place of the speed-controlling screw of the aforesaid Letters Patent, I have substituted the pinion 13 which is fixed on stem i i so that the two rotate together. Stem M is rotatable and slidable in the internal bore of a bushing 15 fixed to the motor housing, and pinion it has a threaded engagement with the bushing It results from this construction that as pinion i3 is rotated stem M is moved up and down to control the position of weight 6-8 relative to the pivot $9. The means for controlling the position of pinion l3 comprises pointer is (Figs. l, 6, and 9) which is connected through hub ll and sleeve 18 with gear "is which in turn meshes with pinion E3. The position of this gear on the sleeve is adjustable by means of set screw Bil. It will be noticed in Fig. i that pinion 13 and gear is have faces sufilciently broad to permit the necessary movement of pinion it in and out to produce the motor-controlling effect above described.

It will be obvious that considerable weight is to be moved in the oscillation of the X-ray tube 36 and the plate holder 22 as previously described. This weight not only includes the parts just mentioned but the heavy column 28 and the lever 2'! and associated parts. Obviously these parts must come to rest and change their direction of travel each time the cross-head pin 62 passes around one of the sprockets or 53. To insure this reversal of movement of these parts with the minimum of wear and shock, I have provided means for slowing down motor 52 where the .55,

cross-head pin 52 makes the reverse bends at opposite ends of its path of travel. To this end, I have provided a resistance 3i (Figs. 4 and 6) in the form of a rheostat mounted on a suitable bracket 82 attached to housing 59. The resistance-selector arm 83 is rotatable with shaft 84 which carries at its upper end a gear 85 which in turn meshes with pinion 85 which is rigidly secured to sleeve it previously mentioned. Provision is made for automatically cutting the resistance 8i into and out of the energizing circuit for motor 52 at the desired points. This mechanism, as best seen in Figs. 2 and '7, comprises a gear Bl, rotatable with shaft 55, driving an intermediate train of gears 8% mounted on a stub shaft 855 and meshing finally with a large gear 98 which in turn is rigidly fixed on jack shaft 9i which is rotatably supported in brackets 92 and 955. On one face of gear ill as best seen in Fig. '7, are fixed a short cam 9d and a longer cam 95. These cams are adapted to engage and operate the blade 36a of a microswitch 96 suitably mounted on one of the brackets. The parts are so arranged. that switch 96 is in its off position as represented by blade 96a in Fig. 18 when the cross-head pin 62 starts its cycle of travel from the position shown in Fig. 2. When the cross-head pin has about reached the top of sprocket 58 at the right-hand end of Fig. 2, short cam 9% moves switch as to the on position as indicated in dot-dash lines in Fig. 18. This continues until the cross-head pin has passed around sprocket 58 and is about to enter the lower run of chain 5'! as viewed in Fig. 2. Then cam t l releases switch blade 96a and the switch automatically returns to ofi position. Just before the cross-head pin reaches the lower side of sprocket 56:3, cam 95 again engages switch blade 96a and returns the switch to on position. The cam 95 then holds switch 96 in this position until the cross-head pin comes to rest at the end of its cycle in the position shown in Fig. 2. This insures not only a slower speed where motion is reversed when the cross-head pin passes around sprockets 56 and 58, but it also insures that all of the heavy parts previously mentioned are moving slowly when the parts come to rest with the cross-head pin and slide in the position shown in Fig. 2. This gives an accurate stopping position of the parts.

lvleans is provided for adjusting the position of the rheostat contact arm 83 in accordance with the setting of the motor governor as controlled by pinion lii. In other words, the connection between gear 19 and pinion 13 on the one hand and pinion as and gear on the other hand is such that the higher the speed set for the governor of motor 52 the greater the resistance selected on rheostat 8| by the setting of arm 83. It results from this construction that practically no resistance on rheostat 8| is cut into the circuit of motor 52 when the slowest governor speed is selected as none is then necessary. But greater amounts of resistance are out in as greater speeds are selected on the governor so as to insure a suiiicient slowing down as the parts reverse their direction of movement at each end of the path of oscillation.

Means is provided for energizing motor 52 as will be later described in connection with wiring diagram Fig. 18 but means will here be described for automatically interrupting said motor energizing circuit when the cross-head and slide have completed a cycle and returned to the position of Fig. 2. To this end there is mounted on jack shaft 9! a stop switch 91 suitably mounted on bracket 93. This switch has a blade llla which is normally in the on position indicated in dotdash lines in Fig. 18 but which is moved to off position by means of a contact cam 98 mounted on jack shaft 535. This cam is best seen in Figs. 5 and 8. This cam has a very short dwell portion so that shortly after the closing of an energizing circuit for motor 52 cam 98 releases switch blade 9111 so that this switch is normally in its on position.

Means is provided for energizing the electrical circuit for X-ray tube 36 while the cross-head pin 62 is traveling from right to left along the lower run of chain til as viewed in Fig. 2. This means comprises an exposure switch 99 (Fig. 4) mounted on a suitable bracket with its switch blade Ella positioned adjacent a cam lull on the end of shaft 9i. The switch 99 may control the exposure of the plate in holder 22 to the rays from tube 36 but preferably it performs th function of the manually operable button 36 shown in Patent 2,267,908, granted December 30, 1941, to Edwin R. Goldfield and Edward B. Graves, so that the resultant exposure is accurately timed as will be readily understood by those skilled in this art.

It is desirable that the number of seconds switch 99 is closed should roughly correspond to and be slightly greater than the desired time of exposure set on the timer of the above-mentioned Goldfield a-nd Graves patent. To this end means is providedfor varying the position of cam I so that switch blade 99a is moved to on position early or late as may be desired during the travel of cross-liead'pin 62 from right to left along the lower run of chain as viewed in Fig. 2.

Referring to Figs. 4, 5, G, and 9, switch 29 is mounted on bracket II]! which in turn is fixed to sleeve I32 which is rotatably mounted on jack shaft 9i. Also fixed on sleeve m2 is beveled gear Hi3 which meshes with beveled gear Iii-I which is fixed onshaft I85 which in turn is retatabiy mounted inan extension of bracket 92 atits lower end and is embraced by sleeve I8 (previously mentioned) at its upper end. The pointer we is fixed to the upper end of shaft I95 and reads on the outermost-scale of Fig. 9 mark-e amplitude. By means of this construction it is possible to rotate switch 98 relative to shaft 9i so that when pointer IE6 is at the end of the scale marked 14 switch 99 is in a position clockwise of the position shown in Fig. 4 whereas when the pointer B06 is at-the end of the scale marked? (Fig. 9) the switch 99 is moved counter clock-wise from the position shown in 4. In otherwords, cam I00 moves in the direction oithe arrowindicated around shaft BI in 4, and when switch 99is moved in a clockwise direction from the position there shown, its blade 99a is engaged b cam Hie sooner and thus the period'oi closure of switch 99 is longer as indicated by the larger numbers on the amplitude scale. The rotation of shaft I95 is limited in one direction by a stop at its upper end (not shown) engaging a suitable pin in the top oi housing 50 while the rotation in the opposite di rection is limited by stop member lieb engaglng one of th wings 567.

During the above description it will have been pose of this cam is to close switch IBS- by means.

of its. operating blade "3S0; at least cneseccnd aliea'dof the closing of switch 9Q. Switch Iilfi is used only when the X-ray tube 36 is provided with a rotating target and is for the purpose of insuring that thetarget" is rotatin when the tube is energized as will be readily understood bythose skilled. in this art. It has no other'conneotion with this invention. The switch 299 is in fixed position and does notrequire any ad-- justment.

The wiring circuit of Fig. 18- will now be de scribed so as to explain how all of the abovementioned functions are carried out. As a preliminary matter it should be explained that the wiring :block I II) is solely for purposes of assembly and testing, and in following th diagrams no reference will be made to this block but the circuits willbe followed directly through the block without further mention. Also in the center of Fig. i there appears a wiring panel Iii which is indicated diagrammatically in Fig. 18, and this panel will be described as it is used in the wiring of our device to X-ray apparatus, supply circuits, etc. A main switch I I2 is indicated on Figs. 2, 9, and 18 and a selective switch H3 for selectinbetween laminography and stereoscopic exposures (explained later) is indicated on Figs. 2, i, 9, and 18.

Referring now to 18, the binding posts L-I, L2 on board Iii are connected to a suitable'source of electric current. It is assumed described back to L2.

th'atlnain switch H2 is closed as indicated and that switch H3 is in the dot-dash position of Fig. 18. The energizing circuit for motor 52 is established through relay II! the circuit for which extends from LI through line I I4, switch I 22, line H5, binding post L3, line I I6, coil I Ila of relay iii, line new binding post PB. A connection is-there establishedby the operator who manually operates push-button H9. This is preferably connected by a suitable cable with the binding posts FBI and PB? and a holding bracket on housing 50 retains th push-button device He in the position shown in Fig. 2 when notin use. Closure of this push-button continues the circuit through binding post PBZ, line I20, line. I25; and switch blade 57a in its oif" positlon, as shown in full lines in Fig. 18, and thence through line main switch IIZ, and line I23 back to L-2. The push-button H9 need be held only an instant to energize relay II'I armature I'llb of which immediately engages contact II'Ib establishing a holding circuit from coil Illa through line Hi l, armature Iiib and line I25 to P32 and so on through the rest of the circuit outlined just above. The energizing of relay II? causes armature II'ic to engage contact H70 and completing the following circuit for motor '52: From Ll through line II4 and switch II2 as before and then through line I28, motor windiIl-g governor contacts 67, motor 52, winding 59, line IZ I, switch H3 in its dot-dash position, lines I25, 528, I29, I35 53!, armature II Ic, line 532, armature II'lb, lines I25, IZfi, IZI, blade 91a, line switch I32, and line 23 to L2.

Upon" very slight rotation of motor 52, cam 98' releases blade 83a of switch 91 whereupon this switch moves to its on position as indicated in dot-dash lines in Fig. 18. The circuit for motor 52 then'run's from Ll to and through line 123 as previously described and thence through blade of rheostat switch so in its full line position Fig. lsand through line I33, bladeS'Ia, line i222, switch" H2, and line I23 to L2. If rheostat switch 950. is in its dotdash position, then the circuit is throughline rheostat BI, selector arm 33, line I35, blade filo, line I22, and so back to L2. Meanwhile the holding circuit for relay coil I I la is from LI through switch II2 and lines H5 and lid as mentioned previously, then through the relay coil II'Ia, lines I24 and I32, armature IIl'c, lines I3I, I30, I29, and thence through blade 95a in either of its positions, through line i233 or IE3 back to L2 as described in the preceding sentence for the motor circuit.

At predetermined points duringthe travel of cross-head pin 52 around the path of chain 57, the rheostat switch 96 is closed and opened as previously described'inconnection with cams 94 and 95. When switch blade 96a is in its dotdash position, the selected resistance of rheostat BI is placed in circuit with the windings of motor 52 so as to slow down the motor speed. At all other times switch blade 98a is in its full line position of Fig. 18 and the motor runs at the governor-controlled speed.

Referring to Fig. 18, when motor 52 reaches sucha speed that the governor-controlled contacts 51 are. opened, the circuit for motor 52 is through line I 25 and winding ?2 as previously described and thence through lines I31, and I38, through-resistors TB, and condenser I39 connected in parallel therewith, and then through lines I49, MI, motor 52, winding II, line I27, switch H3 and the subsequent circuit previously The arrangement of resistors I and condenser I39 serves to muille the arc between contacts 61 which, as previously stated, flutter at high frequency.

Referring to Fig. 18, the exposure switch Q9 when closed by cam I60, as previously described, completes a circuit from binding post K! through lines I42, I43, switch blade 99a and line I i-S to binding post X2. As previously mentioned, a suitable energizing circuit for X-ray tube $6 is con nected with the binding posts XI, X2, and the closing of switch 99 is intended to be analogous to the closing of switch 36 in the above-mentioned Goldfield and Graves Patent No. 2,267,9i s.

The switch I09 when used is closed by cam just ahead of the closing of switch iii and completes a circuit from SI through lines M5, M8, blade IUBa, and lines I41 and I48 to binding post S2. The circuit for energizing the rotating target, when such is used, is connected between these binding posts SI, S2.

My device is so constructed and arranged that it may be used without change for the production of stereoscopic pictures simply by means of throwing switch H3. When this switch is thrown toward S, as indicated in Fig. 9, the

switch is in the full line position of Fig. 1a The circuit for motor 52 is then completed, following actuation of push button H9 and energization of relay coil IIla, from LI through line il i, switch H2, line I25, winding l2, motor 52, winding II, lines I21 and M9, blade Ilia, of stereoscopic switch I58, line lEil, switch IIfi, line I25, and then through line I28 and the following cir cuit back to L2, previously described, until switch 91 moves to its on position and thereafter through switch blade 95a and through line I33 or I34 through blade 91a and back to L2 along the circuits previously described. Stereoscopic switch I5ll has not been previously described but is clearly seen in Figs. 5 and 6. The switch blade ISM is in its on position as indicated in full lines in Fig. 18 when the motor is first energized to start the cross-head pin and slide from the position shown in Fig. 2. The cross-head pin will therefore continue to be moved by chain El and motor 52 until switch blade ISQa is moved to its off position, indicated in dot-dash lines in Fig. 18, by cam l 52 best seen Fig. 8. When switch blade ISlla is moved to its "olf position, the circuit to motor is interrupted and the cross-head slide 63 stops. The magnitude of the stereo-shift just described is approximately onetenth of the focal distance from the X-ray tube target to the body plane to be photographed. This is generally of the order of a few inches. The speed of travel should be set very slow or at 8 on the speed or radially innermost scale where pointer 16 is set in Fig. 9.

This insures that the heavy parts are moving at slow speed and will stop accurately in the pro-- determined position. t will be understood by those skilled in this art that a picture is first taken when the slide 653 is in its initial or starting position as shown in Fig. 2, and after the stereoshift has been made and cam IE2 has caused the parts to come to a stop, a second exposure is made thus giving the two views necessary to pro-- vide a stereoscopic view.

When a stereoscopic exposure has been made as above described, the parts are returned to the initial position shown in Fig. 2 simply by throwing switch H3 to the side marked L and indicated in dot-dash lines in Fig. 18. This completes the circuit through motor 52 again, and the cross-head pin 62 continues on its travel about sprockets 58 and 56 until automatically stopped by switch 9! in the position shown in Fig. 2.

The apparatus is then ready either for anotherstereoscopic operation or for laminography.

In Fig. 17 I have shown a modified manner of mounting the device thus described to produce the same result. Here similar parts have been given similar numbers, and the only difference is that the housing 53 has been mounted on the ceiling and the rod 65 connected with column 28' at the 'point I53 instead of at the point 230. previously described in connection with column 28 of slightly different form. This column 28 is mounted for movement on track I5 i attached to the ceiling or other overhead support and track E55 mounted on or near the floor. The controls connected with housing 50 are provided with downwardly-extending control members I55 and IE1 so that they are within reach of the operator. Other than as just mentioned, the parts are like those previously described and have the same functions and therefore further description is believed to be unnecessary.

The microswitches 95, 91 99, E69, and IE9 are of the type described in U. S. Letters Patent No. 1,960,020 granted May 22, 1934, to P. K. McGall; but any other suitable switch might be used.

What I claim is:

1. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative con: nection between said driving means and said carriage means, an electric motor and associated energizing circuit for moving said driving means at a given speed along a portion of said path between said bends, and means for introducing additional resistance into said motor circuit when said driving means is traversing said reverse bend portions of said path.

2. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at is opposite ends, an operative connection between said driving means and said carriage means, an electric motor and associated energizing circuit for moving said driving means, governor means for holding said motor speed substantially constant, and means for varying said governor means to hold different controlled speeds, whereby the varying conditions of laminography may be met.

3. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative connection between said driving means and said carriage means, an electric motor and associated energizing circuit for moving said driving means at a g ven speed along a portion of said path between said bends, governor means for holding said motor speed substantially constant, means for setting said governor means to hold different motor speeds, means for introducing additional resistance into said motor circuit when said driving means is traversing said reverse bend p0r 11 tions of said path, and means coordinating said last named means and said governor setting means to increase the resistance introduced into said circuit when said governor-controlled speed is increased.

4. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative connection between said driving means and said carriage means, an electric motor and-associated energizing circuit for moving said driving means, and means for introducing additional resistance into said circuit as said driving means approaches a predetermined point, and means for opening said motor circuit when said driving means reaches said point.

5. The combination of claim 1 wherein said additional resistance is retained in said motor circuit as said driving means approaches a predetermined point intermediate said reverse bends, and means for opening said motor circuit when said driving means reaches said point.

6. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a recipr catable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative connection between said driving means and said carriage means, an electric motor and associated energizing circuit for moving said driving means at a given speed along a portion of said path be tween said bends, governor means for holding said motor speed substantially constant, gear operated means for setting said governor means to hold different motor speeds, gear controlled means for introducing additional resistance into said motor circuit when said driving means is traversing said reverse bend portions of said path, and a gear train connecting said gear operated means and said gear controlled means.

7. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising a pair of sprockets, an endless chain passing around said sprockets, elec tric motor means and its associated energizing circuit for driving one of said sprockets, connecting means between said chain and said carriage means, one end of said connecting means mounted on said chain, and means movable in timed relation to said chain for introducing additional resistance into said motor circuit as said connecting means end passes around said sprockets.

8. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative connection between said driving means and said carriage means, means providing substantially uniform linear-motion of said driving means along a portion of said path between said bends, switch means adapted to control energization of said X ray tuba and means for operating said switch 12 means during said uniform movement of said driving means.

9. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous elongated path having reverse bends at its opposite ends, an operative connection between said driving means and said carriage means, an electric motor and associated enerizing circuit for moving said driving meansat substantially uniform speed along a portion of said path between said bends, switch meansadapted to control energization of said X-ray tube, and means for operating said switch means during the travel of said driving means along said portion of said path.

10. The combination of claim 8 including means for setting said last named means with relation to the position of said driving means. along said portion of said path.

11. The combination of claim 9 wherein said last named means is movable in timed relation to the movement of said driving means and end-- jus'table relative thereto.

12. The combination of claim 9 wherein said last named means includes a cam movable in means, said mounted relative to said cam, and means for holding said switch means in different adjusted.

positions relative to said cam.

13. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising electric motor operated driv-- ing means for reciprocating said carriage means, an energizing circuit for said motor, stop means operable in timed relation to said driving means for opening said circuit at a predetermined point of the travel of said carriage means, a secondv energizing circuit for said motor, means for selecting one or the other of said circuits, and stop means for opening said second circuit at a predetermined interval of travel of said carriage means beyond said predetermined point, whereby a stereoscopic shift is provided.

14. The combination of claim 1 wherein said additional resistance is retained in said motor circuit as said driving means passes beyond one of said bends and approaches a predetermined point intermediate said reverse bends, stop means for opening said motor circuit when said driving means reaches said point, a second energizing circuit for said motor, and stop means for opening said second circuit When said drivi-g means has passed a predetermined distance beyond said point.

15. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising a pair of sprockets, a chain in driving relation with said sprockets, a pin carried by said chain, a crosshead slide mounted for reciprocating motion back and forth between said sprockets, said pin reciprocable in said slide, connecting means between said slide and said carriage means, electric motor means for driving one of said sprockets, an energizing circuit for said motor, a rheostat, switch means for cutting said rheostat into and out of said circuit, switch means for interrupting said circuit, switch means 13 adapted to control energization of said X-ray tube, and means operable in timed relation to said driven sprocket for actuating all of said switch means.

16. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising drive means movable in a continuous and complete circuit about a path having separate advance and return runs connected by reverse bends, relatively slidable connecting parts between said drive means and said carriage means providing a continuously operative connection between them along both said advance and return runs, means for slowing said drive means as it approaches a predetermined point between said reverse bends, and means for stopping said drive means when it reaches said point, whereby an exact termination of the cycle of said drive means is always insured.

17. Apparatus for laminography of the type wherein an X-ray tube and a plate holder are mounted on a reciprocatable carriage means for oscillation on opposite sides of a selected body section, comprising driving means movable in a continuous and complete circuit about an elongated path having separated advance and re- 14 turn runs connected by reverse bends at its opposite ends, an operative connection between said driving means and said carriage means adapted to travel about said reverse bends, means operatively associated with said driving means for providing substantially uniform linear motion thereof at a given speed when said connection is traveling along a portion of said path between said bends, and operating means responsive to motion of said driving means for controlling said last named means to reduce the speed of said driving means below said given speed when said connection is traveling around the reverse bend portions of said path.

ROBERT J. STAVA.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,599,395 I-Iards Sept. 7, 1926 1,827,959 Stahelin Oct. 20, 1931 2,156,170 Augustin et al Apr. 25, 1939 2,167,114 Kieffer July 25, 1939 2,235,143 Colcher Mar. 18, 1941 2,353,145 Chamberlain July 11, 1944 

